Method of making brittle metals or alloys



Patented Aug. 4, 1936 PATENT OFFICE METHOD OF MAKING BRITTLE METALS 'OR ALLOYS Walter E. Rcmmers, Western Springs, 111., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York No Drawing. Application May 10, 1934,

. Serial No. 724,912

8 Claims.

This invention relates to a method of making brittle metals or alloys and more particularly to a method of making brittle nickle-iron alloys.

In the manufacture of brittle alloys which are to be pulverized for the purpose of forming the particles into compressed magnetic cores, it has been diflicult to obtain the correct degree of brittleness of the alloys for reducing the ingots cast from the alloys into small particles.

An object of the invention is to provide an effective and simple method of making brittle alloys.

In accordance with one embodiment of the invention, the alloys are first oxidized to a readily determinable degree, after which a predetermined amount of a deoxidizing agent is added to obtain 20 made from insulated and compressed magnetic particles, which may be of a fineness varying in size from particles that willpass through a 100 mesh sieve to particles that will pass through a 300 mesh sieve. In order to obtain these fine particles, the magnetic materials must be embrittled so that when they are cast into ingots and hot rolled, the material will break up into relatively small lumps and the brittleness of the material is also a factor in grinding these lumps into a fine powder. The hot rolling of the ingots is usually accomplished in a mill which has a fixed number of passes. If, for instance, a mill is used having thirteen passes, the ingot must have such a degree of brittleness that it will not 5 crack up appreciably prior to the thirteenth pass and break up into relatively small lumps at the thirteenth pass .from which it is droppedinto a quenching tank. Considerable difliculty has been experienced in obtaining the proper degree of brittleness to break the material into relatively small lumps and cause it to pulverize without requiring 'an undue amount of grinding.

One of the most common materials used for magnetic dust cores is a nickel-iron alloy in which 45 the nickel may vary from 45% to more than 83% of the alloy. Even though these materials, that 'is the nickel and iron, are relatively pure, the nickel usually contains some sulphur and the iron contains fractional percentages of carbon, manga- 50 nese, silicon, sulphur, phosphorus, and some occluded gases, such as carbon monoxide and hydrogen. The sulphur content of the iron is usually quite uniform and ranges from .009% to .012% or over. The nickel and iron are melted 55 together .under a covering of lime and fluorspar slag to which iron oxides are added'either in the form of F8203 or F6304. The iron oxides .tend to oxidize the impurities and gases in the molten alloy and during this oxidation the brittleness of the alloy changes from a state in which 5 it is too ductile or tough to a state in which it is too brittle. The quantity of oxides which must be added varies with the amount and kind of impurities in the iron and nickel used. Obviously other methods of oxidizing the molten bath may 10 be used as the bubbling or blowing of oxygen or air through the bath.

Experience has shown that in practice there is no convenient method of determining and interrupting the process of oxidation at the point of correct brittleness for the subsequent breaking up and pulverizing of the alloy. The applicant has found, however, that there is a determinableand readily recognizable point of oxidation in which the material is too brittle but from which it may be readily returned to the correct degree of brittleness by the addition of a deoxidizing agent. In order to control the brittleness of the alloy, test bars which may be one inch in cross-section and five inches in length are cast from time to time in an open top mold as the process of oxidation progresses. As long as the desired degree of oxidation has not been ob- ,tained, a cross-section of the test bar will disclose fissures and gas pockets, and the surface of the bar will have a spew or ridge of expelled metal extending partly or wholly around the perimeter thereof. This ridge presents a rather interesting and strange-phenomenon since it usually begins along the middle of one or the other of the long sides of the surface and progressively travels around the perimeter, giving it the appearance of a moving worm. When the oxidation has progressed to the desired point, a cross-section of the bar is solid and the ridge no longer appears I on the surface of the test bar but instead the top surface of the bar is relatively flat and may be slightly concave. At this point, considerable additions of oxides to the molten metal cause but slight changes in the brittleness of the alloy. The condition of the bar now indicates that the oxidation has reached a definite point, at which, however, the alloy is too brittle. The alloy may then be returned to any desired degree of brittle: ness by the addition of a known amount of-a 5 deoxidizing agent, such as, for instance, manganese, preferably in the form of ferro-manganese. It is believed that the brittleness is a function of the sulphur contentand the oxygen content or of a combination of the sulphur and oxygen contents. The addition or the term-manganese causes the ridge to reappear'on test bars cast from the alloy and for one specific purpose sufficient term-manganese is added to cause the ridge to extend around one-half of the perimeter of the surface of a test bar. The manganese appears to control the effectiveness of the sulphur content in addition to its action as a deoxidizing agent. Of course, a greater or lesser amount of the deoxidizing agent may be used to cause the ridge to extend to a greater or lesser degree around the perimeter of a test bar, depending upon the brittleness desired in the alloy. Other deoxidizing agents may be used, such as aluminum, silicon, chromium, or magnesium.

In the case of a nickel-iron alloy containing 81% of nickel and the balance substantially iron, sumcient ferro-manganese is added so that the manganese constitutes from approximately .06% to .11% of the alloy by weight. When this alloy is hot rolled'from a temperature of about 2350 F., it is broken up into relatively small lumps with the required number of passes through the rolling mill and the lumps may then be pulverized in an attrition mill and formed into magnetic cores.

It will be understood that the nature and embodiments of the invention herein described are merely convenient and useful forms of the invention and that many changes and modifications may be made therein without departing from the spirit and scope oi! the invention.

What is claimed is:

1. A method of making a'brittle nickel-iron alloy, which comprises adding oxides to the molten alloy to reduce its ductility, testing the alloy progressively as said ingredients are added until a cast specimen of the alloy reaches a predetermined characteristic state having a substantially flat surface, and adding an amount of a deoxidizing agent to produce the desired brittleness insuificient to completely reduce the melt.

2. A method of making a brittle nickel-iron alloy, which comprises adding metallic oxides to a specimen is obtained which issubstantially devoidof a peripheral ridge, and adding a definite amount of manganese, insuflicient to completely reduce the melt.

4. A method of making a brittle nickel-iron alloy, which comprises adding oxidizing materials to the molten alloy, progressively casting test specimens of the alloy as said materials are added until a specimen is obtained having a substantially flat surface, and adding an amount of a deoxidizing agent to produce the desired brittleness.

5. A method of making a brittle nickel-iron alloy, which comprises adding oxidizing materials to the molten alloy, progressively casting test specimens of the alloy as said materials are added until a specimen is obtained being substantially devoid of a peripheral ridge, adding a deoxidizing agent until a specimen is obtained having a predetermined length of peripheral ridge, cast- 20 ing the alloy into ingots, and hot rolling the ingots to break them into fragments.

6. A method of making a brittle alloy, which comprises alloying iron containing sulphur and other impurities with nickel, oxidizing the alloy 25 to embrittle the alloy beyond the extent desired for comminutlng thematerial, progressively casting'test specimens of the alloy until a specimen is obtained being substantially devoid of a peripheral ridge and adding a measured amount of a deoxidizing agent selected from the group of manganese, aluminum, silicon, chromium, and magnesium to obtain the desired degree of brittleness. I

'1. A method of making a brittle alloy, which 35 comprises alloying iron and nickel containing oxidizable impurities, oxidizing the alloy to embrittle the alloy beyond the extent desired for comminuting the material, progressively casting test specimens of the alloy until a specimen is obtained being substantially devoid of the peripheral ridge, and adding a measured amount of a deoxidizing agent to obtain the desired .degree of. brittleness.

8. The steps in the method of embrittling a nickel-iron alloy which comprise adding metallic oxides to the molten alloy until a predetermined characteristic state is reached in which a cast specimen of the alloy is substantially devoid of a peripheral ridge, and adding a predetermined amount of a deoxidizing agent insufficient to completely reduce the melt.

WALTER E. RELIMERS. 

